On one hand I agree with you, on the other hand I don't think the space is short on people writing their own tools. The number of DNS enumerators I've seen shared over the past month alone speaks to this.
If there is a tool/script/exploit/etc out there doing most of what I want, you can be sure that I'm going to use it and modify it to my needs instead of writing my own.
I'd say that's usually the case in 80% of the cases when doing pentests. Besides, time is money.